Swellow, The Swallow Pokémon. If its two tail feathers are standing at attention, it is proof of good health. It soars elegantly in the sky. It dives at a steep angle as soon as it spots its prey. It catches its prey with sharp claws. It circles the sky in search of prey. When it spots one, it dives steeply to catch the prey.

Overview

Swellow is a cool bird. When it was created back in gen 3 it was pretty bad. Like, laughably bad. Diamond and Pearl did wonders for it however with the invention of Toxic Orb, U-turn and Brave Bird. Paired with Guts and Facade this gave Swellow the offensive might of Life Orb Groudon. Swellow hasn't really changed much since then... at all. Sadly though Swellow is very fast and powerful it has almost non-existent defenses. If you let Swellow take a non-resisted STAB hit from basically anything it will probably be knocked out. Swellow also lacks the movepool to do much meaningful damage to basically any Steel or Rock types. Swellow has huge hurdles to overcome to be successful but if you can take down the stone and steel barriers very little will stand in Swellow's way... a feat much easier said than done.Positives
- Guts boosted STAB Facade hits HARD.
- 125 base speed is extremely high. Swellow only has to worried about being beat by Scarfers and priority moves.
- Ghost and Ground immunities plus status "immunity" gives Swellow slightly more chances to switch in than you would expect.

Negatives
- Defense is trash. If Swellow takes any hit it will die.
- Stealth Rock weakness, Toxic Orb, and Brave Bird recoil mean that even if Swellow does not take any hits it probably won't last long.
- A complete inability to hit Rock and Steel types greatly reduces Swellow's ability to sweep teams.
- Predictable. Swellow hasn't changed much in seven years. It does one thing and everyone knows what that thing is.

Abilities

Guts: Attack raises to 1.5 times when induced with a status (BURN, PARALYZE, SLEEP, POISON, FREEZE). BURN’s effect of lowering Attack is not applied. It's difficult to stress how devastating this ability is alongside Facade.
Hidden Ability (Available): Scrappy: A Ghost-type foe can be hit by Normal-type & Fighting-type attacks. Pretty cool, but you give up Guts boosted Facades for the ability to hit Ghosts. You already get Brave Bird, use that. Scrappy is okay but totally outclassed by Guts.

No puns. The set name speaks for itself. Use Protect to wait a turn for Toxic Orb to kick in. This will Poison you and activate Guts which will effectively triple the power of Facade. Brave Bird is the lesser used secondary STAB. It doesn't hit much that Facade doesn't besides Ghosts and the recoil is massive but it is very strong and will OHKO virtually everything it hits super effective. U-turn can do solid damage to incoming Rock types and allow something else of yours a free switch in. U-turn allows some free damage without making you withstand another turn of Toxic damage so it can help keep Swellow alive for a few extra turns. Protect is almost vital for securing a free turn for Toxic Orb to activate but Quick Attack is decent to take out some damaged Scarfers or pick off something with priority before you get hit.

Here are some damage calculations to give you an idea of just how powerful this little bird's Facade can be.

Boomburst, Endeavor, Pursuit, Work Up, Flame Orb, and Steel Wing
While it should never be used as more than a joke set, Choice Specs + Boomburst can be used, especially with Scrappy. Keep in mind though Swellow has only 50 base Attack, so you will only hit for around 2/3rds the damage of Guts Facade. A ton of fun to use, but not actually a good set. Taillow can use Specs Boomburst as a legitimate set if you play Little Cup since Scrappy Specs Boomburst can even 2HKO Misdreavus.Endeavor is interesting because with Scrappy it allows Swellow to hit Ghosts. You can even run a level 1 Taillow with Endeavor and Quick Attack holding a Focus Sash to, in many cases, guarantee a free KO on most Pokemon. Endeavor is also usable on Swellow as it could let you take a counter down with you.Pursuit may catch something frail fleeing from your mighty Facades. However it is very weak.
If Facade is somewhat too weak you can pair it with Work Up to reach pretty scary levels of attack power. Sadly Swellow won't last long enough to be a setup sweeper. Toxic Orb and enemy attacks will kill it long before it can take much down with it.Flame Orb can work over Toxic Orb but almost all of the time Toxic Orb will do less damage per game than Flame Orb.Steel Wing is Swellow's best option against Rock types even if it wont hurt them much.

Double & Triple Battle Options

Swellow is the fastest STAB Guts Facade user in the game. It's 4 base points stronger in Attack than Talonflame and also has Flying type STAB which is a boon in triples. The temptation to abuse that power wilts away when one realizes that Swellow takes Super Effective damage from Discharge, Blizzard and Rock Slide which, thanks to Mega Charizard Y and Gale Wings Talonflame, most, if not all doubles/triples teams will be using. Pair that with the fact that Ghost, Rock and Steel types alongside Intimidate are very common and suddenly Swellow isn't dealing enough damage to warrant using. It is also facing very stiff competition from Talonflame who for the most part does everything Swellow can do but faster.
The best partners for Swellow would be those who have Wide Guard to block off incoming Rock Slides, Discharges, Blizzards. Earthquakes don't bother Swellow nearly as much as it bothers the opposing Rock and Steel types. It might not be a bad idea to run Protect, just in case. It's really a shame it isn't able to combine it's other ability - Scrappy with Guts to hit Ghosts hard. Otherwise it might have a niche that would define itself from Talonflame.

Countering Swellow

Literally any Rock or Steel type in the game. Skarmory, Ferrothorn, Forretress, Aegislash, Registeel, Mawile, Aggron, Magnezone, Steelix, Scizor, Metagross, Jirachi, Empoleon, Bastiodon, Bronzong, Heatran, Bisharp, Klefki, Golem, Omastar, Magcargo, Corsola, Tyranitar, Relicanth, Rhyperior, Gigalith, Carracosta, Barbaracle, and Carbink all easily switch in on any move Swellow will run and KO it back. So yeah, basically every Rock or Steel type completely walk over Swellow. In terms of Pokemon tough enough to just tank a neutral Facade.. well a few Pokemon exist that can do that. Bulky Grounds like Hippowdon, Gliscor, and Landorus can take a few hits and either wait until Toxic brings it down or KO with Stone Edge. Avalugg takes around 30% on average from Guts Facade and can easily KO back and Recover the damage away. Dusclops and Porygon 2 have the eviolite boosted bulk to shrug off a few hits, though Dusclops needs something besides Will-o-Wisp and Night Shade if it plans on beating the bird.
Of course Swellow has no real bulk to speak of so any priority moves will vanquish it forever. Bullet Punch, Mach Punch, Ice Shard, Extremespeed etc. Literally every Choice Scarf user you can imagine should pack the power to KO Swellow in one hit with its STAB moves. Swellow's only hope against these kinds of assaults it Quick Attack, which is fairly weak and isn't too common. Despite being strong and fast Swellow doesn't really match up well against most X/Y teams so it isn't something you should worry all that much about.